Cold plasma enhances sanitizer efficacy against salmonella bacteria on tomato surfaces

Authors: Ukuku, Dike; Mukhopadhyay, Sudarsan; Niemira, Brendan; Olanya, Modesto

Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Consumers’ demand for fresh, healthy, nutritious foods has caused food industries to look for quicker and easier ways of producing foods that are safe, and fresh with minimal or no bacterial pathogens present. Grape tomatoes were inoculated with Salmonella bacteria especially at the stem scar area. Inoculated tomatoes were exposed to cold plasma and antimicrobial solutions developed in our laboratory for up to 380 s. One hundred- and twenty-seconds exposure of individual treatments led to bacterial reduction and when the treatments were combined for 120 s, more bacteria were killed including those attached at the stem scar area. The results suggests that a combination treatment for 120 s, and immediate refrigeration of treated tomatoes will improve the microbial safety of tomatoes designated for fresh-cut salad.

Technical Abstract: Bacterial contamination of fresh produce designated for fresh-cut salad processing continue to be a problem for the produce industry and consumers. To help mitigate this, a solution containing specific organic acids generally recognized as safe (GRAS) was developed in our laboratory and its antimicrobial efficacy was tested alone and in combination with cold plasma on Salmonella bacteria inoculated on tomatoes surface. Tomatoes were spot inoculated or by submersion in 107 CFU/ml Salmonella inoculum for 3 min. Populations recovered after spot inoculation averaged 5.6 ± 0.14 log CFU/ g and 3.9 ± 0.12 log CFU/g for submerged inoculation. Treatments with antimicrobial solution and cold plasma were for 30 s, 60 s, 120 s, 180 s and 360 s, and a combination treatment for 120 s, and 180 s was investigated. Either organic acid or cold plasma treatments for 120 s significantly (P<0.05) reduced Salmonella populations and the surviving populations after treatments for 180 s averaged 1.9 CFU/g for aerobic mesophilic bacteria and < 0.1 CFU/g for yeast, and mold. Similarly, individual treatments with organic acids or cold plasma for 120 s reduced Salmonella bacteria to 2.2 and 1.9 log CFU/g, respectively. Treatment combinations with organic acids plus cold plasma for 120 s and above led to higher bacterial inactivation, and surviving aerobic mesophilic bacteria were reduced to < 0.3 CFU/g after treatments while 4.9 log CFU/g Salmonella bacteria was inactivated. This result suggests that a combination treatment for = 120s to = 180 s is recommended for a higher inactivation of Salmonella bacteria on tomatoes stem scar surfaces.